Field
Various communication systems may benefit from the use of relayed packet data connection. Moreover, such communication systems may benefit from methods and systems for the establishment of a packet data network connection for a proximity services user equipment via a relay user equipment.
Description of the Related Art
The third generation partnership project (3GPP) includes consideration of direct user equipment to user equipment (UE-UE) communication over a long term evolution (LTE) radio interface, even when there is no network coverage. This direct UE-UE communication can relate to Proximity Services (ProSe). Such ProSe services may be used for public safety communication over LTE radio, see section 7 of 3GPP technical specification (TS) 22.278 and 3GPP technical report (TR) 23.703, each of which is hereby incorporated by reference herein in its entirety.
FIG. 1 illustrates a user equipment to network relay scenario. This scenario is one that may be particularly helpful for public safety services. In this scenario, a UE that is out of coverage and supporting direct communication, referred to as ProSe UE 110, can be connected to the network via another UE that is in coverage and supports relaying, referred to as relay UE 120. Although only one ProSe UE 110 is shown, a single relay UE 120 can perform relaying for several ProSe UEs.
One technical issue in scenarios such as this is how the bearer(s) and connection(s) between the ProSe UE(s) 110 and the relay UE 120 are mapped into the bearer(s) and connection(s) between the relay UE 120 and the 3GPP network 130. The service 140 to be provided over the 3GPP network 130 may not necessarily need to know the mechanism, but some mechanism may be needed.
FIG. 2 illustrates bearer sharing. In order to have an efficient solution, the EPS bearer(s) that are between the relay UE 120 and the 3GPP network, such as elements eNB/SGW 230 and PGW 240, can be shared among the ProSe UEs 110a and 110b. As shown in FIG. 2, a single EPS bearer 250 can be used to transfer application data of the different ProSe UEs 110a and 110b, and also data of the relay UE 120 itself. Thus, the EPS bearer 250 is not necessarily limited to carrying the contents of ProSe bearer 260a and ProSe bearer 260b. 
Conventionally, when a 3GPP UE shares its connection among devices, typically over its WiFi interface, is when the UE acts as router. The same approach can be used in a network-to-UE relay scenario.
In this approach, the relay UE assigns the IP addresses to the UEs. Typically with IPv4 the relay UE assigns private IPv4 address to ProSe UEs and performs network address translation (NATting). With IPv6, the relay UE gives either a single IPv6 address to ProSe UEs from the IPv6 prefix it received from the PGW or the relay UE requests a shorter than 64 bit prefix from the PGW via IPv6 delegation, and then assigns a 64 bit prefix to ProSe UEs.
In this approach, the relay UE controls the IP level connectivity of the ProSe UEs, from the network point of view there is only a single IP host: the Relay UE. (Application level control is possible at the network side.) It depends on the Relay UE implementation how the bearers are shared among the ProSe UEs. This type of solution is one of the candidate solutions in TR 23.703.